This invention relates to a tilt device for boat propulsion machines and more particularly to an improved tilt and trim arrangement for a marine drive.
As is well known, marine outboard drives, either the outboard drive of an inboard/outboard arrangement or an outboard motor per se, are supported for pivotal movement about a generally horizontally extending axis. This pivotal movement is provided for two purposes. First, there is a relatively narrow range of trim adjustments provided that will adjust the angle of the propulsion means relative to the watercraft so as to provide the best propulsion means relative to the watercraft so as to provide the best propulsion force for a given running condition. In addition, the tilting movement is such that the outboard drive may be tilted up so that its propulsion means is disposed out of the water during periods of nonuse.
With larger horsepower units, it has been proposed to use a hydraulic motor arrangement for achieving both the trim and tilting movement of the outboard drive. With such arrangements, a relatively more powerful but slower stroke trim fluid motor is employed for achieving the trim adjustment. Since trim adjustments are normally made during running, it is necessary for the trim adjustment motor to have sufficient power so as to offset the driving thrust of the propulsion unit. This results in the relatively low speed operation of the trim adjustment. On the other hand, when tilting the outboard drive up, the fluid motor needs only overcome the weight of the outboard drive and a relatively high speed, low power motor can be used for this purpose.
Because of the differences in stroke and strangth, it has been the practice, in some applications, to employ one or more trim cylinders that are abuttingly engaged with a lower portion of the drive unit for effecting its trim adjustment. When the outboard drive is tilted up, the drive just merely moves away from the abutment with the trim cylinders. Although this simplifies the problem, it can give rise to wear and noise due to the resultant relative movement that is permitted between the outboard drive and the engaging portion of the trim cylinder. In addition, if the trim cylinders are partially extended, there is a likelihood of bending to their piston rods or other components.
In another arrangement, the trim and tilt cylinders operate in series rather than in parallel as in the aforedescribed arrangement. Although this will offset the deficiencies discussed above, it also means that only one fluid motor resists the driving thrust during trim operation and it is necessary to use a larger more powerful trim motor in such applications.
It is, therefore, a principal object of this invention to provide an improved tilt and trim arrangement for an outboard drive that will overcome the aforenoted problems.
It is a further object of this invention to provide a tilt and trim unit for a marine outboard drive wherein two fluid motors may be employed for achieving power trim adjustment without one of the fluid motors restricting the tilting movement and while still permitting a positive connection between the tilt motor and its supporting structure.
The movement of the outboard drive during its trim and tilt positioning has normally been accomplished about a single horizontally disposed axis. Although such an arrangement offers the advantages of providing a relatively simple structure, the movement of the outboard drive between its fully tilted and trimmed down position and its fully tilted and trimmed up position about such fixed horizontal axes causes the propulsion end of the unit to extend a substantial distance behind the transom of the associated watercraft. Thus, when operating in very shallow water with the outboard drive tilted up, the effective length of the watercraft increases significantly. The disadvantages of such an arrangement are discussed in the copending application entitled "Tilting Device For Outboard Engine", Ser. No. 672,410, filed Nov. 16, 1984 in my name and the names of others, which application is assigned to the assignee of this application. The construction shown in that application permits the movement of the outboard drive between a tilted down and a tilted up position without substantially increasing the effective length of the watercraft. In addition, that application shows an arrangement wherein a hydraulic device may be employed for achieving the movement between the respective positions. However, that application and the hydraulic arrangement disclosed in it presents certain of the disadvantages with the hydraulic tilt and trim arrangements aforedescribed for some of the same reasons.
It is, therefore, a still further object of this invention to provide an improved arrangement for supporting and moving an outboard drive between its tilted down trimmed down position and a tilted up trimmed up position.
It is a further object of this invention to provide an improved and simplified arrangement for permitting movement of an outboard drive without significantly increasing the effective length of the associated watercraft when the outboard drive is in its respective positions.